The present invention relates to a device for screwing a cap on to the neck of a container.
Known devices for screwing caps on to the necks of containers are equipped with a plurality of gripper means designed to hold the cap and to screw it on to the neck of the container. In these devices, the gripper means are rotated by appropriate drive means through an adjustable clutch.
Once the cap has been screwed on completely, the clutch through which the rotary motion is transmitted to the grippers, starts slipping when the resistant torque on the gripper means exceeds the value at which the clutch has been set, thus interrupting the connection between the actuating means and the gripper means. The gripper means therefore stop, while the drive means continue to rotate.
At this point, the gripper means are gradually opened to disengage them from the cap and to allow the next container to be fed into the device.
When the gripper means start opening, as soon as the pressure they exert on the side of the cap begins to slacken off, the resistant torque decreases and the clutch restores the connection between the rotary actuating means and the gripper means. As a result, the grippers slide on the side of the cap for a short length before being completely disengaged from the cap. This damages the side of the cap and may give rise to unattractive scoring.
Attempts were made to overcome this problem by coating the gripping surfaces of the grippers with resilient material, such as rubber, for example, in order to protect the side of the cap when the gripper means slide over it but this kind of material wears out quickly and loses its effectiveness in a very short time.
The aim of the present invention is to overcome the disadvantages mentioned above.